Black-legged kittiwake Rissa tridactyla

Status;  International importance;  Population estimates;  Distribution;  Annual abundance/ productivity; Phenology/diet/survival

 

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DescriptionBlack-legged Kittiwake vignette

The following has been adapted from original text by Martin Heubeck in Seabird Populations of Britain and Ireland (with permission from A&C Black, London).

 

As well as being the most numerous species of gull in the world, the black-legged kittiwake is the most oceanic in its habits and most adapted to nesting on vertical rocky sea-cliffs. In Britain and Ireland, the largest and most numerous colonies are found along the North Sea coasts of Britain, around Orkney and Shetland, and off north-west Scotland. Colony size varies from less than ten pairs to tens of thousands, but the locations of colonies tend to be traditional over many decades. Although most colonies are on sheer cliffs, in a few instances man-made structures such as buildings, bridges, sea walls and even offshore oil installations have been utilised. During the breeding season, black-legged kittiwakes feed mainly on small pelagic shoaling fish; around the British Isles these consist of energy-rich species such as sandeels, sprats and young herring. However, kittiwakes will also scavenge for offal and discards around fishing boats, which can be an important food source in years when their preferred prey species are less abundant. Outside the breeding season the species is essentially oceanic, and it is probable that populations from many different breeding localities mix together in the North Atlantic and North Sea during winter, with some birds from British and Irish colonies (especially first-winter and immature birds) spending time off the eastern seaboard of North America.

 


Conservation status

 

Black-legged kittiwake is currently identified as a conservation priority in the following:

EC Birds Directive - migratory species

Red listed in Birds of Conservation Concern 4 (2015 update).

(further information on Conservation Designations for UK Taxa)

Amber listed in Birds of Conservation Concern in Ireland 2014-2019 (2014 update)

OSPAR List of Threatened and/or Declining Species and Habitats

 


International importance

 

UK Population % Biogeographic Population % World Population
378,800 AON* 13.8 (ssp. tridactyla) 8.0

 

*AON = Apparently Occupied Nests

The UK population figure (rounded to the nearest hundred) was derived from data in Mitchell, P.I., Newton, S.F., Ratcliffe, N. and Dunn, T.E. (eds.) 2004. Seabird Populations of Britain and Ireland. Poyser, London. This was also the source of figures for the Biogeographic and World populations.

 


UK population estimates and change 1969-2008

 

Geographical coverage of black-legged kittiwake colonies in the UK was complete during all three national censuses. In some years, in response to a scarcity of food in spring, nest building can be delayed by 2-3 weeks. Under such conditions a high proportion of pairs (up to 40%) may begin nest building but not complete a structure which qualifies as an apparently occupied nest (AON), the preferred count unit, or progress to laying. This phenomenon was documented for Shetland in 2002 but did not affect counts for Seabird 2000. Counts outwith the recommended count period (June) may also underestimate figures but, as this applied to only approximately 5% of UK counts, it is unlikely that such ‘out-of-season’ counts had much influence on gross estimates of population change.

 

 

 Operation Seafarer

(1969-70)

Seabird Colony Register

(1985-88)

Seabird 2000

(1998-2002)

UK Population estimate (AON*)  407,417 504,055 378,847
% change since previous census N/a +24 -25

 

*AON = Apparently Occupied Nests

 


Distribution/abundance

 

The Seabird 2000 census provides the most comprehensive recent assessment of the distribution and abundance of breeding seabirds. Numbers of black-legged kittiwake found in different regions, and a map showing the locations and size of colonies, is provided in the Seabird 2000 black-legged kittiwake results page (PDF, 2.0 mb).

 

An interactive map is available on the NBN Gateway, where you can filter to display only the Seabird 2000 data.  For more recent, but less comprehensive, coverage view the distribution on the NBN with all available contributing datasets.

 

The locations sampled during the annual Seabird Monitoring Programme provide some information on distribution and are accessible via the Seabird Monitoring Programme online database.

 


Annual abundance and productivity by geographical area

 

With reference to the regional accounts below please note the following.

Breeding abundance: graphs of abundance index with 95% CLs are only shown for a region where the trend produced has been deemed accurate (see methods of analysis). Where a trend was thought to be inaccurate, graphs of abundance at major colonies in a region may be shown instead, particularly if such colonies hold greater than 10% of the regional population, are monitored frequently and may thus help illustrate regional population fluctuations outwith national censuses. Occasionally, too few data have been collected regionally to produce either of these.

Productivity: graphs of productivity are only shown if analysis of breeding success data produced a significant result for regional and/or year effects (again see methods of analysis). If results were not significant, then a regional mean productivity value is given. However, on some occasions, too few data are available from which to provide a meaningful average. Furthermore, for 11 species where the quality of monitoring data available was considered high, population viability analysis was undertaken at the UK level and the results of this are also reported.   

 



 

Breeding abundance

 

UK kittiwake abundance trend

Figure 1: Trend in UK abundance index (solid line) of black-legged kittiwake 1986-2015 with 95% confidence limits (dotted lines). Based on SMP data; view the methods of analysis (PDF 158 kb).

 

The UK kittiwake abundance index declined rapidly since the early 1990s, such that by 2015 the index was 60% below what it was in 1986, the third lowest value in 29 years of monitoring (Figure 1). Over the longer term, combining census results with the SMP sample indicates that, while black-legged kittiwake numbers increased by around 24% between the late 1960s and the mid 1980s (see table above), there are probably now around 50% fewer than in the late 1960s. It is likely, given many years of low productivity, coupled with low survival and return rates (see below), that declines will continue.

 

Table 1 shows how numbers have changed at some of the most important UK colonies (those in the SPA network) in the period since they were surveyed for Seabird 2000. Some of the largest declines recorded since Seabird 2000 have been in colonies in the north and north-west. Colonies in Shetland have been declining at an average rate of 11.3% per annum and those in Orkney at an average of 11.6% per annum. Along the east coast of the UK, the average rate of decline is much slower at an estimated 2.6% per annum. In the west of the UK, the average rate of decline is 7.5 per annum.

 

Area SPA Name Seabird 2000 Count (Year) Change (%) % per annum
Shetland Hermaness NNR 643 1999 304 2009 -53 -7.2
Shetland Noss 2,395 2000 179 2015 -93 -15.9
Shetland Foula 1,934 2000 277 2015 -86 -12.2
Shetland Sumburgh Head 877 2001 362 2014 -59 -6.6
Shetland Fair Isle 8,204 2001 859 2015 -90 -14.9
Orkney West Westray Cliffs 33,281 1999 12,055 2007 -64 -11.9
Orkney Copinsay 4,256 1999 955 2015 -78 -8.9
Orkney Marwick Head 5,573 1999 526 2013 -91 -15.5
Orkney Hoy 795 1999 397 2007 -50 -8.3
East Coast Troup, Pennan and Lion's Heads 18,482 2001 14,896 2007 -19 -3.5
East Coast Buchan Ness to Collieston Coast 14,091 2001 12,542 2007 -11 -1.9
East Coast Fowlsheugh 18,800 1999 9,655 2015 -49 -4.1
East Coast Firth of Forth Islands 6,632 2000 7,642 2015 +15 +0.9
East Coast St Abb's Head NNR 11,077 2000 4,209 2015 -62 -6.2
East Coast Farne Islands 5,096 1998 3,956 2015 -22 -1.5
East Coast Flamborough Head and Bempton Cliffs 42,692 2000 37,617 2008 -12 -1.6
West Coast North Rona and Sula Sgeir 4,119 1998 1,253 2012 -70 -8.1
West Coast Handa 7,013 1999 2,715 2013 -61 -6.6
West Coast St Kilda 4,268 1999 277 2015 -94 -15.7
West Coast Shiant Isles 2,006 1999 549 2008 -73 -13.4
West Coast Canna and Sanday 1,274 1999 1,141 2015 -10 -0.7
West Coast Mingulay and Berneray 5,511 1998 1,627 2015 -70 -6.9
West Coast Ailsa Craig 1,675 2001 299 2015 -82 -11.6
West Coast Skomer and Skokholm 2,257 2000 1,546 2015 -32 -2.5
West Coast Rathlin Island 9,917 1999 7,922 2011 -20 -1.9

Table 1: Recent counts of the number of black-legged kittiwake (AON) recorded in SPAs in the UK compared to the number recorded in them during Seabird 2000. The percentage that each colony has fallen by, and the per annum change, is also provided. (Note: data for Hermaness and St Abb's Head relate to only part of the SPA).

 

Given the magnitude of the fall in the index, and the fact that during Seabird 2000 these SPAs held over 50% of the black-legged kittiwakes nesting in the UK, it is possible that the national population now lies between 150,000 and 250,000 AON - far below the figure recorded during Operation Seafarer in 1969-70. Given the declining trend in productivity recorded for much of the period since 1986 (Figure 2), coupled with a falling return rate (Figure 4; assuming this is applicable to other colonies), it is likely that declines will continue.

 

Productivity

 

UK kittiwake productivity trend

Figure 2: Trend in UK productivity (no. of chicks fledged per pair) of black-legged kittiwake 1986-2015. Based on SMP data; view the methods of analysis (PDF 158 kb).

 

Productivity of black-legged kittiwakes in the UK has declined over the course of the SMP (Figure 2), which is related to declines in abundance of their sandeel prey and in certain regions is negatively correlated with sea surface temperatures1, which have risen due to climate change. Productivity (and adult survival) has also been negatively affected by the presence of a sandeel fishery that operated off SE Scotland1. Species such as kittiwakes are particularly vulnerable to food shortages as they can take prey only when it occurs at or near the surface of the sea, unlike diving species such as auks, which have access to a greater variety of prey in the water column. This has exacerbated the effects of low prey abundance. By 2008, on average only one chick was fledged from every four nests, compared with close to one per nest in 1986, 1987 and 1992. This low productivity has probably contributed to the declines in abundance shown above and would indicate that further declines in abundance are likely in the coming years, as fewer chicks become recruited to the breeding population. Productivity of black-legged kittiwakes from 2009 to 2014 was higher than it had been for a number of years, possibly due to high availability of sandeels in those years, but the 2015 breeding season was more typical of those between 2001 and 2006 with few chicks fledged.

 

Analysis of the SMP dataset found mean breeding success at monitored nests in black-legged kittiwakes was 0.68 and has declined at a rate of 0.02 chicks per nest per year2. This equated to a decline in success of 31% over the study period 1986-2008. The quality of the dataset meant a change in breeding success greater than 5% would be detected with high confidence. Using available life history information (population size, clutch size, age at first breeding and survival rates of different age classes) to develop population viability analysis, it was predicted that if this level of breeding success is maintained, populations of black-legged kittiwakes would be expected to decline by 35% over the next 25 years. In order to prevent such a decline, breeding success would need to increase to around 1.50 chicks fledged per nest2.

 

 

Population estimates and change 1969-2002 (census data)

 

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998-2002)

Population estimate (AON*) 346,097 359,425 282,213
% change since previous census    N/a +4 -21

 

* AON = Apparently Occupied Nests

 

Breeding Abundance

 

Scotland kittiwake abundance trend

Figure 1: Trend in abundance index (solid line) of black-legged kittiwake in Scotland, 1986-2015 with 95% confidence limits (dotted lines). Based on SMP data; view the methods of analysis (PDF 158 kb).

 

Over the long-term, census results indicate numbers in Scotland changed little between Operation Seafarer and the Seabird Colony Register, but fell thereafter so that Seabird 2000 recorded 21% fewer nests than the SCR. Data collected by the SMP indicate a steady decline since the late 1980s, with the index in 2014 72% below the 1986 baseline (a slight rise compared to the low point in 2013 when the index was 78% lower than in 1986).

 

Productivity

 

Scotland kittiwake productivity trend

Figure 2: Trend in productivity (no. of chicks fledged per pair) of black-legged kittiwake in Scotland, 1986-201. Based on SMP data; view the methods of analysis (PDF 158 kb).

 

Black-legged kittiwakes breeding in Scotland show a sustained decline in productivity since 1986, culminating in a very poor breeding season in 2008 when few chicks fledged. Productivity between 2009 and 2015 was higher than it had been for a number of years, possibly due to increased availability of sandeels in those years. However, this increased production was not sustained; 2013 was again a poor breeding season.

 

 

Population estimates and change 1969-2002 (census data)

 

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998-2002)

Population estimate (AON*) 49,676 125,819 76,281
% change since previous census    N/a +153 -39

 

* AON = Apparently Occupied Nests

 

Breeding Abundance

 

England kittiwake abundance trend

Figure 1: Trend in abundance index (solid line) of black-legged kittiwake in England, 1986-2015 with 95% confidence limits (dotted lines). Based on SMP data; view the methods of analysis (PDF 158 kb).

 

In England, the peak in abundance index was reached in 1992 (cf. 1989 in Scotland). A gradual decline is apparent after 1995, but over much of the last decade the index has been relatively stable, although falling in recent years. The abundance index has not fallen to the extent seen in Scotland but - in 2015 - lay at 35% below the 1986 baseline. Another difference between the two countries is that between Operation Seafarer and the Seabird Colony Register the English population more than doubled, as opposed to showing little change, but the proportional size of decline from the Seabird Colony Register to Seabird 2000 was nearly twice that recorded to the north. Causes of change are probably the same for both countries (see UK section) but are clearly now having a greater impact in Scotland where the estimated rate of decline is greater.

 

Productivity

 

England kittiwake productivity trend

Figure 2: Trend in productivity (no. of chicks fledged per pair) of black-legged kittiwake in England, 1986-2015. Based on SMP data; view the methods of analysis (PDF 158 kb).

 

Productivity at English colonies, usually more successful than those in Scotland, has been generally decreasing since 1986. The low point was reached in 2004 when productivity averaged just 0.37 chicks per nest, but has improved since. Monitored colonies were least productive in 1998, 2004, 2008 and 2013. However, 2009 to 2012 inclusive were four of the more successful breeding seasons in the last decade. After an increase in the previous year, productivity fell slightly in 2015 (0.74 chicks fledged per pair). 

The relatively high productivity in England compared to Scotland, despite a declining trend, may explain why the species' abundance has not fallen to the same extent. The reasons for higher mean productivity in English colonies is not clear, though they do not appear to have encountered the periodic extreme food shortages that have befallen some Scottish colonies, especially those in the Northern Isles.

 

 

Population estimates and change 1969-2002 (census data)

 

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998-2002)

Population estimate (AON*) 6,891 8,771 7,293
% change since previous census    N/a +27 -20

 

* AON = Apparently Occupied Nests

 

Breeding Abundance

 

Wales kittiwake abundance trend

Figure 1: Trend in abundance index (solid line) of black-legged kittiwake in Wales, 1986-2015 with 95% confidence limits (dotted lines). Based on SMP data; view the methods of analysis (PDF 158 kb).

 

National censuses found that numbers had changed little between Operation Seafarer and Seabird 2000, but recent measures of abundance suggests the current population is probably lower than in 1969-70. Factors affecting colonies in other countries in the UK, appear to have less of an impact in Wales but the reasons for this are not well understood. Compared with Scotland, the abundance index for black-legged kittiwakes in Wales has been relatively stable since 1986, but is similar to that shown for England with a slow decline since the mid-1990s. However, in recent years the index has fallen below the previous low point in 2004. Currently, the index is 35% below the 1986 baseline; 11 colonies surveyed in 2015 held 4,353 AON, 44% fewer than was recorded at the same colonies during Seabird 2000 (6,230 AON).

 

Productivity

 

Wales kittiwake productivity trend

Figure 2: Trend in productivity (no. of chicks fledged per pair) of black-legged kittiwake in Wales, 1986-2015. Based on SMP data; view the methods of analysis (PDF 158 kb).

 

The productivity of black-legged kittiwakes in Wales has fluctuated widely over the recording period with no clear trend, although productivity appears to have been depressed over much of the last decade. In general, Welsh colonies are less productive than those in England and there are more years when productivity falls below 0.50 chicks per pair compared with both England and Scotland. Productivity in 2012 and 2013 was particularly low in Wales, although details as to why were limited. On Skomer (Dyfed), one of four colonies regularly monitored, low breeding success in 2012 was partly attributed to storm damage. In 2013, 132 fewer black-legged kittiwakes nests were built in study plots on the island compared to 2012 (632), with the breeding season described as disrupted, unusually extended and unsynchronised. Complete failure, of 70 AON, was recorded in one plot although the other two plots fledged one chick for approximately every two nests. In 2014, productivity was 0.63 and in 2015 it had increased to 0.79 chicks fledged per pair.

 

 

Population estimates and change 1969-2002 (census data)

 

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998-2002)

Population estimate (AON*) 4,753 10,040 13,060
% change since previous census    N/a +111 +30

 

* AON = Apparently Occupied Nests

 

Breeding Abundance

 

There are approximately 13 colonies of black-legged kittiwake in Northern Ireland, but few are monitored regularly. The largest colony is Rathlin Island (Co. Antrim) which held 76% of the national population, some 9,917 AON, during Seabird 2000. In 2007, numbers there were similar, with 9,896 AON recorded. However, numbers had declined by 2011 to 7,922 AON (a fall of 20%)3. Seven smaller colonies (The Gobbins, Muck, Portrush (all Co. Antrim), Maggie’s Leap (Co. Down), Castlerock and Portrush (both Co. Londonderry)), visited in 2015 held 1,265 AON compared to 1,085 AON during Seabird 2000. Forty-four additional AON were counted at Mussenden (Co. Londonderry not counted during Seabird 2000)4. Populations at individual colonies are fluctuating, presumably in response to local feeding conditions. It seems that the black-legged kittiwake population of Northern Ireland has slightly increased since Seabird 2000; however, a survey of Rathlin Island is needed to really understand what is happening to the Northern Ireland black-legged kittiwake population.

 

Productivity

 

Northern Ireland kittiwake productivity trend

Figure 2: Trend in productivity (no. of chicks fledged per pair) of black-legged kittiwake in Northern Ireland, 1986-2014. Based on SMP data; view the methods of analysis (PDF 158 kb).

 

In Northern Ireland, few data on the productivity of black-legged kittiwake have been collected as part of the SMP. Data were sparse before 1997, with productivity thereafter extremely variable, so no clear trend was visible. Breeding success at one colony, The Gobbins, was especially low in 2014 due to predation by a mixed pair of hooded Corvus cornix and carrion crows Corvus corone which constantly harassed nesting adult black-legged kittiwakes; many depredated eggs were found in cliff-top caches5. Only 29 chicks fledged from 121 monitored nests at this colony. Low productivity in several years since 2005 may now be contributing to the fall in numbers recorded at some colonies. In 2015, productivity was much improved at The Gobbins with 1.03 chicks fledged per nest4.

 

 

Population estimates and change 1969-2002 (census data)

 

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998-2002)

Population estimate (AON*) 39,630 34,180 36,100
% change since previous census    N/a -14 +6

 

* AON = Apparently Occupied Nests

 

Breeding Abundance

 

In the Republic of Ireland, Operation Seafarer found 39,630 AON of black-legged kittiwake. Numbers had decreased slightly by the second national census, but Seabird 2000 recorded similar numbers to the Seabird Colony Register. However, in 2015, cliff‐nesting seabirds were counted at 28 colonies; the majority of these were Special Protection Areas. A total of 21,576 compared to 32,935 AON during Seabird 2000 were recorded, representing a decline of 34%6. These colonies held 91% of the national population during Seabird 2000, hence changes measured from such large sample are representative of the national trend indicating that black-legged kittiwake numbers are in decline.

 

Productivity

 

Eire kittiwake productivity trend

Figure 1: Trend in productivity (no. of chicks fledged per pair) of black-legged kittiwake in the Republic of Ireland, 1986-2015. Based on SMP data; view the methods of analysis (PDF 158 kb).

 

Black-legged kittiwakes in the Republic of Ireland have had few years with high levels of productivity. In most years, productivity lies below 0.80 chicks fledged per pair and often falls below 0.60. Productivity was lowest in 2008, which was a wet summer in Ireland that possibly impacted on young birds in nests; high intensity monitoring at Dunmore East (Co. Waterford) revealed a clear loss of chicks as the breeding season progressed. 

 

 

Population estimates and change 1969-2002 (census data)

 

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998-2002)

Population estimate (AON*) 44,383 44,220 49,160
% change since previous census    N/a <-1 +11

 

* AON = Apparently Occupied Nests

 

Breeding Abundance

 

In the whole of Ireland, Operation Seafarer and the Seabird Colony Register both recorded a little over 44,000 AON of black-legged kittiwake. Numbers had increased by 11% to 49,160 AON by the time of Seabird 2000.

 

During Seabird 2000, Rathlin Island held 76% of the national population however, in 2015 only a small proportion of colonies were monitored. Seven smaller colonies visited in 2015 held 1,265 AON compared to 1,085 AON during Seabird 2000, an increase of 17%. On the contrast, in the Republic of Ireland, colonies that held 91% of the national population during Seabird 2000, were counted in 2015. A total of 21,576 compared to 32,935 AON during Seabird 2000 were recorded, representing a decline of 34%6. In the whole of Ireland, it seems that black-legged kittiwake numbers are declining since Seabird 2000; however, a survey of Rathlin Island is needed to really understand what is happening to the Northern Ireland black-legged kittiwake population. 

 

Productivity

 

All-Ireland kittiwake productivity trend

Figure 1: Trend in productivity (no. of chicks fledged per pair) of black-legged kittiwake throughout Ireland, 1986-2015. Based on SMP data; view the methods of analysis (PDF 158 kb).

 

The trend in breeding productivity of black-legged kittiwakes throughout Ireland is similar to that shown for the Republic of Ireland where most data have been collected. There are few years when productivity is higher than 0.80 chicks fledged per pair. Particularly poor breeding seasons were recorded in 1996 and 2008, probably due to a wet summer in the latter year impacting on young birds in nests. Such low levels of productivity may now be having a deleterious effect on abundance. 

 

 

Population estimates and change 1969-2002 (census data)

 

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998-2002)

Population estimate (AON*) 908 1,376 1,045
% change since previous census    N/a +51 -24

 

* AON = Apparently Occupied Nests

 

Breeding Abundance

 

kittiwake Calf of Man abundance 2015

Figure 1: Abundance of black-legged kittiwake on the Calf of Man (Isle of Man), 1986-2013.

 

Full censuses recorded 908 black-legged kittiwake AON during Operation Seafarer, increasing by 50% to 1,376 AON during the Seabird Colony Register. A decline then occurred with Seabird 2000 recording just over 1,000 nests. Only one colony, the Calf of Man, has been counted recently and numbers there have fallen drastically. During Seabird 2000, 182 AON were recorded at this colony in 1999, declining to 104 AON in 2006 but only 8 AON were recorded in 2010, 5 AON in 2011 and 13 AON in 2013. No data have been submitted for 2014 and 2015. In light of this large decline, coverage of other colonies is desirable to ascertain the species’ current status on the Isle of Man.

 

Productivity

 

No data have been collected recently, but between 1986 and 2005 there was no statistically significant effect of year in the breeding productivity of black-legged kittiwakes nesting on the Isle of Man; an average of 0.27 chicks were fledged per nest each year. 

 

 

Population estimates and change 1969-2002 (census data)

 

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998-2002)

Population estimate (AON*) 12 34 3
% change since previous census    N/a +183 -91

 

* AON = Apparently Occupied Nests

 

Breeding Abundance

 

The black-legged kittiwake had only a small breeding presence in the Channel Islands. Three nests were recorded during Seabird 2000, 34 during the Seabird Colony Register when the population was at its peak and 12 nests during Operation Seafarer. In 2015, a survey of the Isles of Scilly found 75 AOS on St Agnes, a decrease of 73% from Seabird 20002.

 

Productivity

 

No systematic data on the productivity of black-legged kittiwakes on the Channel Islands have been submitted to the SMP.

 

 


UK phenology, diet, return rates and survival rates

 

Phenology

 

No systematic data on phenology (timing of life-cycle events) have been collected as part of the SMP.

 

Diet

 

kittiwake Isle of May diet 2015

Figure 3: Percentage of sandeels (by weight) in the diet of young black-legged kittiwakes at the Isle of May (North-east Fife), 1987-2015.

 

Sandeels are an energy-rich food source compared with some alternative prey and the proportion of sandeels by weight may be used as a measure of 'diet quality'. Figure 3 shows that the percentage of sandeel in the diet of black-legged kittiwakes on the Isle of May has been low for most years in the period 2006-2015; in these years, sprat Sprattus sprattus, rockling and gadids comprised most of the remainder by weight of their diet. Snake pipefish Entelurus aequoreus were taken in some abundance between 2005 and 2008, though they contributed very little in terms of weight and are of low food value7. Sandeels comprised a high proportion of the diet of Isle of May kittiwake chicks in 2009, 2012 and 2014 and productivity there and UK-wide was high in those years. Kittiwake diet is also sampled at Canna (Lochaber). In 2015, 28 food samples were analysed from regurgitations collected from black-legged kittiwakes between 6th and 9th July. These mainly comprised roughly equal amounts of sandeel and gadoid, with only a few containing clupeids and crustacea8. No trends in diet composition are evident over the course of the SMP on Canna. 

 

Return rates and survival rates

 

Important notes on interpretation:

Estimation of kittiwake adult return rate and survival rate is currently undertaken at two sites within the SMP - the Isle of May (south-east Scotland) and Skomer (south-west Wales). Return rates are based on sightings of individually colour-ringed birds and calculated as the proportion of marked birds present in year one that is seen in the following year. Because not every adult alive is seen each year, return rates for 2015 presented here for Isle of May need to be treated as minimum estimates of survival of birds seen in 2014. In contrast, survival estimates - as presented here for Skomer - do take into account birds that are not seen one year but which re-appear in following years.

 

kittiwake Isle of May return 2015

Figure 4: Annual return rate of black-legged kittiwakes breeding on the Isle of May (North-east Fife), 1987-2015.

 

The return rate of black-legged kittiwakes on the Isle of May (Figure 4) declined between 1986 and 1998 and has typically fluctuated at a low level since then. Particularly low rates occurred in 2007-2009 but in 2010 the return rate (89.0%) was the highest since 1989 and well above the average for the period prior to this (77.7, 95% CI =74.5-81.0). In 2015, the return rate of black-legged kittiwakes (84.1%) was still above average but slightly reduced (1986-2014 average 78.4%, 95% CI =75.6-81.2). Adult survival was negatively affected by the presence of  a sandeel fishery that operated off south-east Scotland1 between 1990 and 1999.

 

kittiwake Skomer survival 2015

Figure 5: Estimated adult survival rate of black-legged kittiwakes on Skomer (Dyfed), 1986-2014.

 

Survival rates of kittiwakes on Skomer (Figure 5) declined between 1991 and 1996 and then increased up to 2001, after which another decline is evident. The survival rate in 2007 was particularly low. The survival rate of breeding adult kittiwakes in 2013-14 was 0.73, a considerable decline. Over the period of the long-term study (1978-2014), survival of breeding adults averages 0.84. There continues to be wide fluctuation in adult breeding survival between years, despite a high probability of re-sighting live birds (>90% encounter probability in the last ten years). There appears to be a degree of correlation between survival rates on Skomer and return rates on the Isle of May (Figure 4), suggesting that similar conditions during the non-breeding season may affect both populations. A recent study using geolocation data loggers to examine the non-breeding season distribution of kittiwakes found tagged birds from Skomer (and Rathlin) remained relatively near the colony but those from the Isle of May dispersed more widely with the main areas of use split between the North Sea and the Central and West Atlantic6,9.

 


References

1 Frederiksen, M., Harris, M.P., Daunt, F., Rothery, P. and Wanless, S. 2004. The role of industrial fisheries and oceanographic change in the decline of North Sea black-legged kittiwakes. Journal of Applied Ecology 41: 1129-1139.

2 Cook, A.S.C.P. and Robinson, R.A. 2010. How representative is the current monitoring of breeding success in the UK?BTO Research Report No. 573, BTO, Thetford.

3 Allen, D., Archer, E, Leonard, K. and  Mellon, C. 2011. Rathlin Island Seabird Census 2011. Report to the Northern Ireland Environment Agency.

4 Leonard, K. and Wolsey, S. (eds.). 2016. Northern Ireland Seabird Report 2015. British Trust for Ornithology, Thetford.

5 Leonard, K. and Wolsey, S. (eds.). 2015. Northern Ireland Seabird Report 2014. British Trust for Ornithology, Thetford.

6 Newton, S.  Lewis, L. and  Trewby, M. 2015. Results of a Breeding Survey of Important Cliff‐Nesting Seabird Colonies in Ireland 2015. National Parks and Wildlife Service Ireland.

7 Harris, M.P., Newell, M., Daunt, F., Speakman, J., and Wanless, S. 2007. Snake pipefish Entelurus aequoreus are poor food for seabirds. Ibis 150: 413-415.

8 Swann, R.L., Aiton, D.G., Call, A., Foster, S., Graham, A., Graham, K and Young, A. 2016. Canna seabird studies 2015. JNCC Report 474l, Peterborough.

9 Frederiksen, M., Moe, B., Daunt, F.,Phillips, R.A, Barrett, R.T., Bogdanova, M.I., Boulinier, T., Chardine, J.W., Chastel, O., Chivers, L.S., Christensen-Dalsgaard, S., Clément-Chastel, C., Colhoun, K., Freeman, R., Gaston, A.J., González-Solis, J., Goutte, Grémillet, D., Guilford, T., Jensen, G.H., Krasnov, Y., Lorentsen, S.-K., Mallory, M.L., Newell, M., Olsen, B., Shaw, D., Steen, H., Strøm, Systad , G.H., Thórarinsson T.L. and Anker-Nilssen, T. 2012. Multicolony tracking reveals the winter distribution of a pelagic seabird on an ocean basin scale. Diversity Distribution 18: 530-542.

 


Partners

Data have been provided to the SMP by the generous contributions of its partners, other organisations and volunteers throughout Britain and Ireland. Partners to the SMP are: BirdWatch Ireland; The British Trust for Ornithology; Centre for Ecology and Hydrology; Natural Resources Wales; Department of Environment, Food and Agriculture (Isle of Man); Department of Environment, Heritage and Local Government (Republic of Ireland); States of Guernsey Government; JNCC; Manx Birdlife; Manx National Heritage; The National Trust; National Trust for Scotland; Natural England; Northern Ireland Environment Agency; The Royal Society for the Protection of Birds; Scottish Natural Heritage; Seabird Group; Shetland Oil Terminal Environmental Advisory Group; Scottish Wildlife Trust.  More about the SMP partners >>

 

Image of black-legged kittiwake appears courtesy of Ian Rendall ©is subject to international copyright law and may not be reproduced in any form whatsoever.

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